Chief prosecutor Bekir Sahiner speaks to the media in the coal miners’ town of Soma, Turkey, Sunday, May 18, 2014. Twenty-five people, including mining company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.(AP Photo/Emre Tazegul)

Chief prosecutor Bekir Sahiner speaks to the media in the coal miners’ town of Soma, Turkey, Sunday, May 18, 2014. Twenty-five people, including mining company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.(AP Photo/Emre Tazegul)

Chief prosecutor Bekir Sahiner speaks to the media in the coal miners’ town of Soma, Turkey, Sunday, May 18, 2014. Twenty-five people, including mining company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.(AP Photo/Emre Tazegul)

Miners close an entrance to their coal mine in Soma, Turkey, Sunday, May 18, 2014. Eighteen people, including company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.(AP Photo/Depo Photos)

Police officers secure the area at the entrance of sub-governor office of coal miners’ town of Soma, Turkey, Sunday, May 18, 2014. Eighteen people, including mining company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday. The banner reads: ” Police, crime site, no entry.”(AP Photo/Emre Tazegul)

Police officers stand outside the local courthouse in the coal miners’ town of Soma, Turkey, Sunday, May 18, 2014. Twenty-five people, including mining company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.(AP Photo/Emre Tazegul)

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SOMA, Turkey (AP) â€” Sensors noted high levels of toxic gas inside a coal mine days before the Turkish mining disaster that killed 301 workers but company officials took no action, Turkish news reports said Monday.

Prosecutors, meanwhile, formally arrested two more people for the devastating mine fire in the western town of Soma, raising the number of suspects facing charges of negligent death to five. Those detained included executives and supervisors at mine owner Soma Komur Isletmeleri A.S., prosecutors say.

Chief prosecutor Bekir Sahiner said 25 people were initially detained as part of the probe, but several were released without charges while eight others were released but could be charged later. Authorities were still questioning the company’s CEO, Can Gurkan, the state-run Anadolu Agency reported.

The Hurriyet, HaberTurk, Milliyet and other Turkish newspapers said prosecutors and inspectors probing the worst mining disaster in Turkey’s history had seized data from the mine that indicated sensors showed high gas levels inside the mine as early as two days before the May 13 disaster. The reports say company officials did not record these high levels on log books and took no precautionary actions.

The Turkish newspapers did not cite source for their reports. Sahiner did not answer calls and no one picked up telephones at the prosecutors’ office in Soma or in the nearby city of Akhisar, which is leading the probe.

But miners who survived the disaster also told The Associated Press that supervisors ignored rising gas levels and failed to take precautionary measures.

Sahiner said Saturday that a preliminary probe indicated that coal had been smoldering days before the disaster, causing the roof to collapse in one part of the mine and unleashing toxic gases that spread throughout.

Government and mining officials have both said that most victims died from toxic gases released by the fire. They have insisted, however, that the mine was inspected regularly and negligence wasn’t a factor in the fire.